The field of the invention is systems and methods for spatially encoding nuclear magnetic resonance signals, such as may be used in magnetic resonance imaging (“MRI”).
Interventional procedures such as the crossing of chronic total occlusions (“CTOs”) using a wire could benefit a great deal from new imaging methods that enable the visualization of the device and the vessel wall during the procedure. This would be an improvement over the current x-ray methods for which the vessel is not visible due to a lack of blood flow. MRI has been proposed as a solution, but has not yet become widely used. One problem with using MRI for these applications is that there is a lack of interventional devices that enable imaging at the high spatial resolution required to adequately image the vessel wall and lumen.
In conventional MRI systems, magnetic field gradients are established to spatially encode nuclear magnetic resonance signals emanating from the volume-of-interest being imaged. These magnetic field gradients are stationary relative to physiologic movements occurring within the volume-of-interest. Thus, compensation for this motion either must be performed prospectively by limiting the times at which data is acquired to those times when little to no motion is occurring, or must be performed retrospectively by correcting the acquired data for the effects of the motion that occurred during data acquisition. In cardiac MRI, compensation for motion typically requires data acquisition during short quiescent periods where the heart is approximately motionless.
These limitations and problems are removed if the magnetic field gradients used to spatially-encode the nuclear magnetic resonance signals are able to move with the physiologic motion, such that a local frame of reference is created. Thus, there is a need to provide a system and method for spatially-encoding nuclear magnetic resonance signals in a local frame of reference, such as one that is allowed to move separately from an MRI system.